The present invention relates to a process for computing dyeing and printing recipes in accordance with a given reference shade by defining each hue of a reference shade as colour position in a colour space, and, in accordance with these data of said colour space, matching each hue from a single dye, from a mixture of two dyes or from a mixture of three dyes.
All sectors of industry engaged in colouring must carry out colour matching with reference shades or to make new colour and design combinations. In recent years technological advance in this branch of industry has been substantial as a result of the linkage of design, coloured computer graphics, colorimetry and computer stations.
It is possible at the present rime to display a reference shade or pattern on a monitor using a scanner or video camera and to vary it, as desired, with respect to form and colour and also to print this design on to any substrate using a colour printer, for example an ink-jet printer. Matching the reference shade however, still poses problems, as the desired shades have to be selected from a comprehensive colour atlas. Collections of up to 15,000 different shades are known, as are also computer-assisted systems which are able to store a very large number of shades which can be displayed on a monitor or printed on to any substrate using a colour printer. The traditional electronic colour atlases provide the recipes for each class of dye, which may differ from one substrate to another.
Creating such colour atlases is very troublesome and time-consuming. The colour atlases are naturally only valid for as long as the basic dyes, the methods of application and and the substrates do not change. Any change necessitates an at least partial or even complete recreation of the colour atlas. This procedure is therefore extremely uneconomic.
Colorimetric match predictions by means of spectrophotometry are also known. This kind of recipe formulation also has deficiencies when colour matching, as the known programs are insufficiently selective and usually provide a host of recipes, so that specialists have to be called in to choose the "right" recipes from these suggestions. A trial dyeing is then prepared from these selected recipes and then corrected once or more than once, according to the experience of the specialist.
All colorimetric systems which are at present known and used in practice for matching a reference shade use reflectance curves of the reference shade and the attempt is made, by mixing known dyes, to approximate to the reflectance curves of the reference shade.
Because the reflectance curves are dependent on the dyes, and as it is normally not possible to use the dyes used in the reference shade, the matching will generally have a reflectance curve which deviates more or less from the reference shade. To keep the deviation as small as possible, mixtures of different dyes are used, thereby compensating for differences in the reflectance curves. This procedure is time-consuming and requires great experience with the dyes used.